# Open Abdominal Aortic Aneurysm Repair

## Overview

Open surgical repair of an abdominal aortic aneurysm (AAA) involves excising the aneurysmal segment of the aorta and replacing it with a prosthetic graft. This procedure was first successfully performed by Charles Dubost in 1951 and later refined by Michael DeBakey and Denton Cooley. Despite advances in endovascular techniques, open repair remains the definitive and most durable treatment for AAA. When performed electively at high-volume centers, perioperative mortality ranges from 2 to 5%. Long-term durability is excellent, with over 90% of patients free from reoperation at 10 years, which is superior to outcomes seen with endovascular aneurysm repair (EVAR).

## Indications

Open repair is indicated for AAAs measuring 5.5 cm or larger in men and 5.0 cm or larger in women. Rapid aneurysm growth exceeding 1 cm per year also warrants intervention. Symptomatic AAAs presenting with pain, tenderness, or distal embolization require repair regardless of size. Anatomical factors that preclude EVAR, such as a short proximal neck, severe angulation, or inadequate vascular access, favor open repair. Young, fit patients often benefit from open repair due to its superior durability. Additionally, open repair is preferred when concurrent open surgery is needed, such as renal or mesenteric revascularization, or in cases of failed prior EVAR requiring late conversion.

## Preoperative Assessment

### Cardiac Risk

AAA repair is classified as a high-risk surgical procedure with a cardiac risk exceeding 5%. According to the ACC/AHA perioperative guidelines, assessing functional capacity is crucial; patients with a functional capacity of 4 metabolic equivalents (METs) or greater are considered low risk. The Revised Cardiac Risk Index (RCRI or Lee Index) helps stratify risk further. Stress testing is reserved for situations where the results would alter management. Routine coronary revascularization prior to AAA repair does not improve outcomes, as demonstrated by the CARP trial. Echocardiography is indicated if there is clinical suspicion of valvular heart disease or left ventricular dysfunction. Medical optimization includes continuing beta-blockers if the patient is already on them and initiating statins.

### Pulmonary Assessment

Pulmonary function tests are recommended for patients with respiratory symptoms. Smoking cessation should be encouraged at least 4 to 8 weeks before surgery to reduce pulmonary complications. Patients should be instructed in incentive spirometry to improve postoperative lung function. The retroperitoneal surgical approach may be preferred in patients with severe chronic obstructive pulmonary disease (COPD) due to its lower pulmonary morbidity.

### Renal Assessment

Baseline renal function should be evaluated with serum creatinine and estimated glomerular filtration rate (eGFR). Patients with renal insufficiency require a hydration protocol to minimize perioperative renal injury. Planning for suprarenal aortic clamping is essential when indicated, as it increases renal ischemia time and risk.

### Vascular Anatomy

Computed tomography angiography (CTA) is the gold standard for preoperative planning. It allows detailed assessment of the proximal neck anatomy, including length, diameter, angulation, presence of thrombus, and calcification. Evaluation of the renal arteries, iliac arteries, and access vessels is critical for surgical strategy.

<image>Preoperative CT angiography with 3D reconstruction showing an infrarenal abdominal aortic aneurysm with measurements of the proximal neck length, neck diameter, aneurysm diameter, and relationship to the renal arteries and iliac bifurcation for surgical planning</image>

## Surgical Approaches

### Transperitoneal (Midline)

The transperitoneal approach via a full midline laparotomy extending from the xiphoid process to the pubis is the standard technique for most AAA repairs. This approach is familiar to most surgeons and provides excellent exposure of the right renal artery and both iliac systems. It facilitates addressing the aortic bifurcation and bilateral iliac aneurysms and allows inspection of the bowel. However, it is associated with higher pulmonary morbidity due to diaphragmatic splinting, increased incidence of postoperative ileus, more painful recovery, and a 10-20% risk of incisional hernia.

### Retroperitoneal (Left Flank)

The retroperitoneal approach involves a left flank incision from the tip of the 11th or 12th rib to the left rectus muscle. The aorta is accessed by retracting the peritoneal contents medially. This approach offers better exposure for suprarenal or juxtarenal aneurysms, allowing suprarenal aortic control. It results in less pulmonary morbidity and postoperative ileus and is preferred in patients with a hostile abdomen due to prior laparotomy or stoma. It may also permit earlier extubation. However, it provides limited access to the right renal artery and right iliac system, making aortobifemoral reconstructions more challenging. Patients may experience flank bulge or denervation.

| Feature | Transperitoneal (Midline) | Retroperitoneal (Left Flank) |
|---------|--------------------------|------------------------------|
| Incision | Xiphoid to pubis midline laparotomy | Left flank, tip of 11th/12th rib to rectus |
| Best for | Standard infrarenal AAA; bilateral iliac disease | Juxtarenal/suprarenal aneurysms; hostile abdomen; severe COPD |
| Advantages | Familiar exposure; access to right renal artery and both iliacs; bowel inspection | Less pulmonary morbidity; less ileus; earlier extubation; suprarenal control |
| Limitations | Higher pulmonary morbidity; more ileus; incisional hernia (10–20%) | Limited right renal/right iliac access; flank bulge/denervation |

## Operative Technique

The operation begins with exposure by retracting the transverse colon cephalad and eviscerating the small bowel to the right, followed by incision of the posterior peritoneum overlying the aorta. Proximal control is typically achieved with an infrarenal aortic clamp placed below the renal arteries. Suprarenal clamping is reserved for juxtarenal or pararenal aneurysms, while supraceliac clamping may be necessary for suprarenal aneurysms or emergency situations. Distal control involves clamping the common iliac arteries bilaterally or the external/internal iliac arteries if iliac aneurysms are present. Systemic heparinization with 80-100 units/kg is administered before clamping.

A longitudinal aortotomy is made in the aneurysm sac, and mural thrombus and debris are evacuated. Back-bleeding lumbar arteries are oversewn from within the sac to prevent bleeding. The inferior mesenteric artery (IMA) is assessed for back-bleeding; it should be reimplanted if pelvic circulation is compromised or if the sigmoid colon appears ischemic.

Graft selection depends on the extent of disease. A tube graft (aorto-aortic) is used if the iliac arteries are not aneurysmal or severely diseased, offering the fastest and simplest repair. A bifurcated graft (aortobiiliac or aortobifemoral) is chosen when iliac disease is present. The proximal anastomosis is performed end-to-end using 3-0 or 4-0 polypropylene sutures, typically in a continuous fashion. Distal anastomoses are fashioned end-to-end or end-to-side depending on the graft configuration.

Reperfusion is achieved by sequential clamp release to avoid hypotension, releasing one limb at a time and coordinating with anesthesia for volume loading before unclamping. Hemostasis is meticulously checked at all suture lines. The bowel, especially the sigmoid colon, is inspected for viability due to the risk of ischemic colitis. Finally, the aneurysm sac is closed over the graft to prevent aortoenteric fistula formation.

### Graft Materials

Dacron (polyester) grafts are the most commonly used materials and come in woven or knitted forms. Woven Dacron has lower porosity and less bleeding through the graft wall, making it preferred in emergency settings. Knitted Dacron is more compliant and allows better tissue incorporation but requires preclotting or impregnation with collagen or gelatin. Polytetrafluoroethylene (PTFE) grafts are an alternative but are less commonly used for aortic replacement. Rifampin-soaked grafts are employed in contaminated fields or for secondary prevention of graft infection. Typical graft sizes are 16-20 mm for tube grafts and 14x7 or 16x8 mm for bifurcated grafts.

## Physiology of Aortic Clamping

Clamping the aorta proximal to the aneurysm has significant physiological effects. Above the clamp, systemic vascular resistance (SVR) increases by 40-60%, leading to increased afterload, hypertension, and elevated myocardial oxygen demand. Left ventricular wall stress rises, increasing the risk of myocardial ischemia or failure. The severity of these effects depends on the clamp level, with infrarenal clamping causing less impact than suprarenal or supraceliac clamping.

Below the clamp, ischemia affects the lower extremities, which can generally tolerate 30-60 minutes of infrarenal ischemia. Suprarenal clamping causes renal ischemia, and ischemia time should be limited to under 30 minutes if possible; cold crystalloid renal perfusion may be used for longer durations. Supraceliac clamping induces visceral ischemia, which should be minimized. Spinal cord ischemia is rare with infrarenal clamping but poses a risk with suprarenal or supraceliac clamping.

Upon unclamping, a sudden decrease in SVR and central hypovolemia occurs, accompanied by washout of vasoactive metabolites such as lactate, potassium, and myoglobin, leading to declamping hypotension. Prevention strategies include gradual clamp release, volume loading, and vasopressor support, with close communication between the surgical and anesthesia teams.

<image>Intraoperative photograph of an open AAA repair showing the aorta clamped infrarenally, the opened aneurysm sac with mural thrombus being evacuated, and a Dacron tube graft ready for proximal anastomosis with labeled key structures</image>

## Perioperative Management

Postoperatively, patients are typically admitted to the intensive care unit for 1 to 3 days of monitoring. Hemodynamic monitoring includes arterial line and central venous catheter placement. Urine output should be closely observed, aiming for greater than 0.5 mL/kg/hr. Serial lactate measurements help assess tissue perfusion. A nasogastric tube is maintained until bowel function returns. Deep vein thrombosis prophylaxis is essential. Pain management may involve epidural analgesia, especially if a retroperitoneal approach was used, or patient-controlled analgesia (PCA). Early mobilization is encouraged to reduce complications.

## Complications

### Early

Myocardial infarction is the leading cause of perioperative death, occurring in 2-5% of cases. Hemorrhage may result from anastomotic bleeding or coagulopathy. Acute kidney injury occurs in 5-10% of patients, particularly with suprarenal clamping. Ischemic colitis affects 1-7% of patients, most commonly involving the left colon and sigmoid colon. Risk factors include ligation of the IMA without reimplantation, occlusion of hypogastric arteries, and intraoperative hypotension. Clinical signs include bloody diarrhea, leukocytosis, and acidosis postoperatively. Diagnosis is confirmed by flexible sigmoidoscopy. Mild cases may be managed conservatively, but transmural necrosis requires surgical resection, which carries a mortality exceeding 50%. Lower extremity embolization, known as "trash foot," can occur from distal emboli. Spinal cord ischemia is rare with infrarenal clamping, occurring in less than 0.5% of cases.

### Late

Late complications include incisional hernia, which occurs in 10-20% of patients after midline laparotomy. Anastomotic pseudoaneurysms develop in 1-5% of patients within 5 to 10 years. Aortoenteric fistula, occurring in 0.5-2% of cases, typically involves the duodenum and presents with a herald gastrointestinal bleed followed by massive hemorrhage. Computed tomography may reveal gas around the graft and loss of the tissue plane between the graft and bowel. Treatment involves graft excision, bowel repair, and either extra-anatomic or in-situ reconstruction. Graft infection is a devastating complication occurring in 1-2% of patients. Sexual dysfunction, such as retrograde ejaculation, may result from autonomic nerve injury at the aortic bifurcation.

## Open AAA Repair vs. EVAR: Long-Term Perspective

The EVAR-1 trial demonstrated that EVAR has lower perioperative mortality but loses its survival advantage by two years, with higher rates of reintervention and aneurysm-related death during long-term follow-up. The OVER and DREAM trials showed no significant difference in long-term survival between open repair and EVAR. Open repair offers superior durability with fewer late reinterventions. Therefore, the choice between open repair and EVAR must be individualized based on aneurysm anatomy, patient fitness, and preferences.

## Clinical Pearls

Cardiac risk assessment is the most critical component of preoperative evaluation because myocardial infarction remains the leading cause of perioperative mortality. Communication with the anesthesia team before clamping and unclamping is essential, as these are the highest-risk moments during surgery. Inspecting the sigmoid colon before closing is vital since missed ischemic colitis at the initial operation carries a mortality greater than 50%. The inferior mesenteric artery should be reimplanted if there is no back-bleeding, if the superior mesenteric artery is occluded, or if both hypogastric arteries are occluded. Wrapping the graft with the aneurysm sac and interposing omentum between the graft and duodenum helps prevent aortoenteric fistula. The retroperitoneal approach is preferred for juxtarenal aneurysms and patients with hostile abdomens or severe COPD. Young, fit patients benefit from the durability of open repair, as the graft will likely outlast the patient.

<image>Diagram comparing tube graft (aorto-aortic) and bifurcated graft (aortobiiliac) configurations for open AAA repair, showing proximal and distal anastomotic sites with indications for each configuration</image>

## References
- Chaikof EL, et al. SVS practice guidelines for the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018;67(1):2-77.
- Lederle FA, et al. Long-term comparison of endovascular and open repair of abdominal aortic aneurysm (OVER trial). N Engl J Med. 2019;380(22):2126-2135.
- Patel R, et al. Endovascular versus open repair of abdominal aortic aneurysm in 15-years' follow-up of the UK EVAR trial 1. Lancet. 2016;388(10058):2366-2374.
- Hertzer NR, et al. Open infrarenal abdominal aortic aneurysm repair: the Cleveland Clinic experience. J Vasc Surg. 2002;35(3):550-557.
- McFalls EO, et al. Coronary-artery revascularization before elective major vascular surgery (CARP trial). N Engl J Med. 2004;351(27):2795-2804.